The relationship between proton temperature and momentum flux density per unit mass at 1 AU is examined using Helios 1 solar wind data from 1974 to 1980. In high-speed plasma (V>500 km s-1) Tp increases with increasing noV2, where no and Tp are the density and proton temperature at 1 AU and V is the flow speed. In low-speed plasma (V<500 km s-1), Tp does not increase with increasing no V2, and perhaps tends to decrease slightly. These basic relationships between Tp and no V2 are not significantly affected by stream interactions. A qualitative explanation of these results is offered in the context of a solar wind model that includes deposition of momentum and energy extending well outward into the interplanetary medium.